Two-wheel drive two-wheeled vehicle

ABSTRACT

A two-wheel drive motorcycle having a drive train that supplies power to the front wheel and includes a series of rigid shafts or other internalized drive systems. The front wheel drive consists of components located on the axis of steering within the head tube and positioned symmetrically in a counterbalancing fashion within the front fork in order to counteract the torque reactions from the rotating front wheel drive while providing a full range of steering. The front wheel drive lengthens and shortens in parallel with the shock-absorbing front fork. An engagement clutch, a one-way hub, and torque limiting clutch operatively engaged with the front wheel drive are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. application Ser. No.10/187,984, filed Jul. 3, 2002, entitled “Two-Wheel Drive Two-WheeledVehicle,” which is a Divisional of U.S. application Ser. No. 09/631,982,filed Aug. 3, 2000, entitled “Two-Wheel Drive Two-Wheeled Vehicle,” nowU.S. Pat. No. 6,439,592, which is a continuation-in-part of U.S.application Ser. No. 09/372,160, filed Aug. 11, 1999, now U.S. Pat. No.6,182,991, which is a continuation-in-part of application Ser. No.09/171,742, filed Oct. 23, 1998, now U.S. Pat. No. 6,161,854, which is a371 of PCT/US97/06181, filed Apr. 25, 1997 and relates to and claims thebenefit of U.S. Provisional Application Ser. No. 60/016,232, which wasfiled on Apr. 26, 1996. In addition, application Ser. No. 09/372,160relates to and claims the benefit of U.S. Provisional Application Ser.No. 60/096,264, filed Aug. 12, 1998. Each of the above referencedapplications are incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a two-wheel drive two-wheeled vehicle,and more particularly a two-wheel drive motorcycle having a rear wheeldriven by a chain or shaft mechanism and the front wheel driven by aseries of shafts and gears transferring power to the front wheel fromeither the motorcycle transmission or the driven rear wheel. Moreover,the two-wheel drive motorcycle disclosed herein is configured so thatthe front wheel drive components counterbalance all steering systemtorque reactions and moments of inertia through placement of numerouscomponents located on the axis of steering and symmetrically within themotorcycle front fork. The novel configuration enable the rider tomaintain control of the two-wheel drive motorcycle during thehigh-speed, high-power rotation of the engine-powered front wheel drive.

2. Description of Related Art

As motorcycle and off-road motocross riding has gained broader appeal,the demands that riders place on their vehicles have increaseddramatically. Conventional motorcycles are powered through a chain orshaft linking the engine to the rear wheel. However, motocross andmotorcycle riders are now facing riding conditions and obstacles wherehaving only rear wheel drive can lead to vehicle damage, loss of controland an unstable front wheel during cornering and off-road riding ingeneral. For professional riders, precious race time is lost avoidingobstacles or losing traction in loose rocks, sand, dirt, mud, or ice.Traction and climbing ability are severely limited in extreme mountainconditions by only having the rear wheel provide power. Accordingly,there is a need in the industry for a two-wheel drive motorcycle thatefficiently and safely transfers power from the motor through thetransmission to the front wheel, that provides the rider with increasedability to safely negotiate rough terrain, and that does not detractfrom the aesthetic qualities, appearance or function of the motorcycleitself.

While both two-wheel drive motorcycles and two-wheel drive bicycles havebeen attempted in the past, the present invention relating to thetwo-wheel drive motorcycle offers significant technical and functionalinnovations previously not disclosed or anticipated. The presentinvention features symmetrically positioned and counterbalanced frontwheel drive components relative to the axis of steering and motorcyclecenterline that eliminate or minimize the torque reactions that wouldotherwise adversely affect motorcycle control when the front wheel isdriven. Additionally, the present invention illustrates a front wheeldrive for a two-wheel drive motorcycle that is completely enclosedwithin the motorcycle frame, head tube, and front fork in a way thatreduces danger to the rider from moving parts and ensures that themotorcycle steering is unencumbered.

By comparison, previous attempts at constructing a two-wheel drivemotorcycle have utilized hydraulic, hydrostatic, and variations of belt,shaft or chain drives that have numerous exposed parts. Importantly,none of the previous attempts at constructing a two-wheel drivemotorcycle would result in a functional two-wheel drive motorcycle.Primarily, none of the prior attempts have taken into account that amotorcycle drive system based upon rigid shafts can spin at severalthousand revolutions per minute producing torque reactions along thefront fork from the spinning front wheel drive system that would resultin an uncontrollable pull on the front wheel. Furthermore, previousattempts have failed to provide a motorcycle with a full rage ofsteering.

U.S. Pat. No. 4,702,340 shows a motorcycle with a front wheel driven bya chain supported by the motorcycle fork and handlebars powering a largechain drive gear on the front wheel. The patent is assigned to RokonInternational who previously produced a similar two-wheeled vehiclecapable of only low-speed rough terrain maneuvering. As shown, the frontwheel drive chain would severely limit the ability to manufacture amotorcycle capable or any high speed maneuvering.

U.S. Pat. Nos. 5,014,808, 5,050,699, 5,054,572, and 5,113,964 showvariations of motorcycles with a front wheel powered by a series ofbelts, chains, gears, or sprockets from the motor to the front fork andthen to the front wheel along one side of the fork. While a motorcycledoes not need the same broad range of steering that is necessary for abicycle, the presence of a bulky drive chain on one side of themotorcycle would cause problems with both steering as well as unwantedtorque reactions that would make the motorcycle potentiallyuncontrollable at high speeds. The exposed front wheel drive chains alsopose a potential hazard to the rider.

U.S. Pat. Nos. 5,873,428 and 5,894,903, JP9156570A2, EP 0 779 205 A2,and EP 0 779 205 A3 show motorcycles with a front wheel driven byhydraulic motors or hydrostatic pressure from the engine to the frontwheel. A motorcycle with a front wheel driven by a hydraulic drivesystem would have significantly less efficient power transfer than arigid-shaft drive system.

GB Patent Number 1,284,821 shows a motorcycle with a front wheel drivenby an extremely complex shaft and gear drive system. The motorcycleincludes a radically-redesigned front end without a head tube, verylarge gears extending well in front of the axis of steering, and a frontdrive system located within one fork leg. The adverse torque reactionsresulting from the unbalanced front wheel drive system and high-speedrotation of the front wheel drive would likely result in a motorcyclethat is uncontrollable. This configuration of the front wheel drivewould also prevent a full range of steering.

WO 93/09992 (PCT/FR92/01084) discloses a front wheel drive for atwo-wheel drive motorcycle that is not counterbalanced on the axis ofsteering and is located in a significantly enlarged front end lacking ahead tube. Such a front end would interfere with the full steering rangeof the motorcycle during sharp turns and make the motorcycle impossibleto ride on complex terrain and potentially pose a safety risk.Additionally, while the invention discloses a drive system within bothfork legs, the invention fails to disclose a counter-balanced drivesystem as several gears are vertically offset from each other. Further,as illustrated, the dimensions of a standard motorcycle would requirethat the drive gears be several inches in diameter and both the shaftsand gears are inadequately supported for the enormous torque that wouldbe transferred through such a drive system design. In short, thedisclosed two wheel drive vehicle fails to adequately address theproblem of torque counter balancing or provide a full range of steering.

The attempts at constructing two-wheel drive two-wheeled vehicles alsoinclude several two-wheel drive bicycle designs. Generally, two-wheeldrive bicycles fall into two categories: 1) permanent designs involvingdrive trains attached to the frame, and 2) retrofit kits which convertexisting bicycles to two-wheel drive. The main drawbacks to thesesystems are: 1) a modification to the standard bicycle in the form of akit is expensive when considered as an addition to a bicycle purchase,2) the low strength flexible shaft limits the allowable loading on thesystem, 3) the retro-fit kit requires considerable skill to attach andcannot be designed to optimally work with every frame design, and 4) thedrive mechanisms are often large and openly exposed on the outside ofthe frame potentially creating additional hazards for the rider anddetracting from the overall appearance of the bicycle. In short, none ofthe two-wheel drive bicycles discussed below could be successfullymodified or adapted to produce a functional two-wheel drive motorcycle.U.S. Pat. No. 4,773,662 shows a bicycle with a front wheel driven by achain connected to a handlebar mounted hand pedaling system. The bicycleuses arm power to drive the front wheels and is adaptable to aconventional bicycle frame.

U.S. Pat. No. 5,542,689 shows a front wheel drive system for a bicyclewhich can be installed on a bicycle to drive the front wheel by rockingthe handlebars back and forth. As with U.S. Pat. No. 4,773,662 mentionedpreviously, this bicycle attempts to harness the energy of the rider'sarms as an additional power source for driving the bicycle. However, adrive mechanism requiring the use of the riders arms for more thansteering, balance and control of the vehicle would likely create safetyproblems and interfere with the bicycle's operation for bothprofessional and recreational mountain bikers.

U.S. Pat. No. 5,052,705 describes a bicycle with power distribution fromthe rear wheel to the front wheel via a caliper and cable drive system.The drive system is activated by a caliper clamped on the rear wheelconnected by a cable to a caliper on the front wheel. Inefficient powertransfer to the front wheel due to slippage as well as torque loss inthe cable would likely be a problem with this system.

U.S. Pat. No. 5,224,725 describes one permanent system that has beendeveloped utilizing a series of chains and sprockets. This designutilizes many moving parts that would make the bicycle very awkward anddifficult to maintain. The exposed chain that runs along the top tubecould be hazardous to the rider and the front chain also would interferewith steering.

U.S. Pat. No. 5,324,057 describes a bicycle driven with a chain meshedwith both the front and rear sprockets through a plurality of gears,pulleys and spring systems to power the front wheel.

U.S. Pat. Nos. 5,332,244, 5,253,889, 5,158,314, 5,116,070, and 4,895,385disclose two-wheel drive bicycles including a front wheel driven byflexible cables or flexible cables in combination with chains. Othersystems, such as the system produced by Turner Drive Systems of Rogers,Arkansas, target the market for a drive system which can be retrofit toany standard bicycle frame with modifications primarily to the gearingand chain attachments necessary to drive the front wheel. As discussedabove, a cable-driven front wheel results in inefficient power transferto the front wheel due to cable wind.

U.S. Pat. No. 5,332,244 discloses chain-sprocket arrangements, alongwith a flexible shaft to transmit some of the power from a rear gearboxto the front wheel. The retrofit system utilizes the inner most sprocketfor the drive system, however the rider can use the other sprockets toshift gears normally. Deformation of the flexible cable, andcorresponding loss of efficient power transfer from the rear wheel tothe front wheel is a drawback of each of these systems when compared tothe rigid shaft drive of the present invention.

U.S. Pat. No. 5,158,314 uses a complex mechanical system to power thefront wheel from the powered rear wheel. A first traction chain coupledto the rear wheel and attached to the frame is connected to a series ofrigid and flexible shafts which attach to a second traction chain whichis mounted above and powers the front wheel. U.S. Pat. No. 4,029,332 andU.S. Pat. No. 4,474,660 also describe two-wheel drive bicycles withcomplex chain or belt drive and pulley systems.

Bicycle hubs utilizing roller clutch bearings are described in U.S. Pat.Nos. 5,485,905 and 5,662,197. However, neither application discloses theuse of the roller clutch hub to provide power transmission advantagesfor the front wheel drive of a two-wheel drive bicycle nor does eitherutilize more than a single roller clutch within the hub for addedstrength and durability of the hub shell.

SUMMARY OF THE INVENTION

The present invention is a two-wheel drive motorcycle, otherwise knownas an all wheel drive motorcycle or a motorcycle powered by both therear and the front wheels simultaneously. The two-wheel drive motorcycledisclosed herein may include a shock-absorbing front fork or rearsuspension system. Additionally, the front wheel drive of the two-wheeldrive motorcycle may be adapted to a number of motorcycle frameconfigurations including motocross, enduro, road, cruising and touringmotorcycles.

The disclosed embodiments of the two-wheel drive motorcycle are noveland inventive over all prior two-wheel drive motorcycles and two-wheeldrive bicycle attempts. The two-wheel drive motorcycle disclosed hereinis configured so that the front wheel drive components counterbalanceall steering system torque reactions and moments of inertia.Furthermore, the two-wheel drive motorcycle of the present inventionincludes numerous components located on the axis of steering within thehead tube. The two-wheel drive motorcycle disclosed herein featurespaired components, gears, and drive shafts positioned symmetricallyrelative to the centerline and axis of steering (in a mirror-likefashion) within the motorcycle lower crown and front fork. The two-wheeldrive motorcycle of the present invention has a full-range ofuninterrupted steering enabling the rider to maintain control of thesteering of the two-wheel drive motorcycle during the high-speedrotation of the engine-powered front wheel drive.

The two-wheel drive motorcycle of the present invention includes a headtube that encloses a front wheel drive and includes a separated necktube that supports the front fork and steering mechanism on bearingswithin the head tube to enable rotation of the steering mechanism aroundthe front wheel drive gears.

The two-wheel drive motorcycle of the present invention includes a rigidshaft front wheel drive supported by bearings and, therefore, does notexperience the inefficient power transfer to the front wheel of otherpreviously-disclosed front wheel drive systems.

The two-wheel drive motorcycle disclosed herein further includes a rigidfront wheel drive that powers the front and rear wheels instantaneously,without power loss, and in a ratio which enables safe and effectiveoperation of the motorcycle and provides instantaneous transfer of powerfrom the motor to the front wheel.

The two-wheel drive motorcycle of the present invention further includesa motorcycle frame and front fork that substantially enclose the frontwheel drive within the head tube and fork of the motorcycle providingeffective power transfer to the front wheel with no interference ofrider motion, with normal braking and steering radius, and with minimalrider danger from moving parts.

The two-wheel drive motorcycle disclosed herein further includes a frontwheel drive that may be adapted to a variety of common motorcycle frameconfigurations and designs including motocross, enduro, road and touringmotorcycles.

The two-wheel drive motorcycle of the present invention furtheroptionally includes an engagement clutch in the front wheel drive thatallows the rider the option to choose between rear-wheel-only drive,two-wheel drive, or front-wheel-only drive operation when conditionswarrant.

The front wheel drive technology of the present invention may optionallybe incorporated into a shock-absorbing front fork and rear suspensionsystem of a motorcycle to provide the rider with a smoother ride.Sliding spline shafts supported by ball or needle bearings allow forsmooth operation of the front fork with minimal friction from thesliding shafts as the front for expands and compresses.

The two-wheel drive motorcycle disclosed herein also optionally includesa free wheeling front hub that utilizes a roller clutch bearing, or anyother type of ratcheting clutch, or sprag clutch bearing. Additionally,in one alternative embodiment, the free wheeling hub includes atorque-limiting clutch to prevent failure of the front wheel drive underextreme torque loads.

The two-wheel drive motorcycle disclosed herein further proposesalternative drive systems that can be incorporated into the frame, headtube and front fork of the motorcycle or within tubing attached to theframe to power the front wheel either from the rear wheel or directlyfrom the engine and transmission in the center of the motorcycle. Onesuch alternative front wheel drive features a ball-bearing drive system.

The two-wheel drive motorcycle disclosed herein further proposes the useof a torque limiting clutch that can be incorporated into the frontwheel drive system to relieve excess torque transmitted through thedrive system from the motor.

The present invention, as specifically described in the first and secondembodiments, has several novel and innovative features when compared toall previously attempted two-wheel drive motorcycles and bicycles,including the two-wheel drive bicycle disclosed in related applications.First, the two-wheel drive motorcycle disclosed herein is configured sothat the front wheel drive components counterbalance steering systemtorque reactions and moments of inertia. Second, the two-wheel drivemotorcycle disclosed herein includes numerous components located on theaxis of steering within the head tube to minimize or negate any torquereactions that could negatively affect steering and control as power istransferred to the front wheel.

The two-wheel drive motorcycle disclosed herein features paired orcounterbalancing and symmetrical components, gears, and drive shaftspositioned relative to the axis of steering and centerline within themotorcycle lower crown and front fork to minimize or negate torquereactions that could negatively affect steering and control as power istransferred to the front wheel. The two-wheel drive motorcycleconfigured with symmetrical drive shafts and components in the frontfork and head tube as disclosed herein facilitates a full-range ofuninterrupted steering while enabling the rider to maintain controlduring the high-speed rotation of the engine-powered front wheel drive.

Unlike the previously disclosed two-wheel drive bicycles andmotorcycles, this invention discloses a front wheel drive for atwo-wheel drive motorcycle that includes components and at least twofront wheel drive gears located on the steering axis within themotorcycle head tube. Additionally, the two-wheel drive motorcycledisclosed herein optionally incorporates the front wheel drive withinthe head tube and a neck tube that is severed, or features a cut-awaysection. However, any front wheel drive that contains components alongthe axis of steering either within the head tube or in the vicinity ofwhere a typical head tube would be located between the fork members iscontemplated by the present invention.

Additionally, it is desirable to place the rotating front wheel drivecomponents along the steering axis above the front wheel so that thereis limited tendency to produce rotational torque to the front wheelduring normal and high-speed operation. Moving the front wheel drivecomponents even a small amount off the steering axis could result intorque reactions that would make steering difficult. Furthermore,placing the drive components symmetrically along each side of the frontfork, thus, rotating in opposite directions, provides a counterbalancingeffect to offset the torque reactions. The front wheel driveconfiguration of the present invention provides stability to themotorcycle and enables steering and operation at all speeds.

Additional features of the two-wheel drive motorcycle disclosed hereininclude a front wheel drive that transfers power to the front wheel fromgears originating within the motorcycle's transmission or from gearslocated at the rear wheel. The front wheel drive may include rigidshafts and meshing gears or a number of other drive components andassemblies, including ball bearing drives, that are internalized withinthe motorcycle frame and that minimize power loss when powering thefront wheel without limitation of the steering range. A two-wheel drivemotorcycle in accordance with the present invention provides a riderwith increased safety and the ability to significantly increase speedduring navigation through dangerous stretches of terrain.

The two-wheel drive motorcycle of the present invention further uses aseries of rigid shafts as the main power transfer means to the frontwheel. Rigid shafts have the advantage of virtually instantaneous powertransfer, whereas flexible shafts usually have from 10 to 20 degrees ofrotational displacement when subject to a torque which would lead to aspongy feeling. Similarly, hydraulic drives are not as efficient as arigid drive system in transferring power through the system.Additionally, a rigid shaft drive is supported by bearings which resultsin very low friction in the front wheel drive system.

The front wheel drive system of the two-wheel drive motorcycle of thepresent invention is substantially enclosed either within the frame orwithin tubing attached to the frame, within the head and neck tubes,and/or within the front fork crown and fork tubes to maintain the frontwheel drive in a fixed position thereby minimizing or eliminatingslippage and, as importantly, enclosing the moving parts to minimizedanger to the rider. Enclosing the front wheel drive system will alsomaintain the general aesthetic appearance of the motorcycle. Priortwo-wheel drive motorcycles and bicycles featured numerous externaldrive chains to the front wheel that significantly detracted from theappearance. Enclosing the front wheel drive within the head and necktubes and modifying the neck tube to accommodate the front wheel drivewhile turning enables the motorcycle steering mechanism to turn smoothlywithout interference with the front wheel drive system. Finally,enclosing the front wheel drive facilitates adaptation to numerouscommon motorcycle frame designs including motocross, road, and touring.

The front wheel hub of the two-wheel drive motorcycle of the presentinvention is designed to attach meshing gears. More specifically, thepower is transferred to the front wheel from the motorcycle'stransmission or rear wheel through a rigid drive system that includesgears located on the lower end of the symmetrically-positioned driveshafts located within each fork tube and that mesh with gears mounted oneither side of the front wheel hub. The gears may feature eitherstraight or helical (spiral) gear teeth although helical gears arepreferred for strength, smoothness and quieter power transfer.

The head and neck tube or the steering axis region of the motorcycle ofthe present invention are modified to accommodate at least three meshinggears with one being attached to the front end of the main drive shaftthat originates at the motorcycle's transmission or from the rear wheeland the other two being attached to drive shafts which attach to gearslocated within the lower fork crown. The meshing gears are supported onbearings within the head tube to keep the bearings and front wheel drivecomponents aligned along the steering axis. The disclosed configurationfurther provides an optimum fork angle relative to the ground forsteering responsiveness and control without restricting steering of thetwo-wheel drive motorcycle. The head and neck tubes, which may be eitherstandard sized or enlarged, are modified so that the neck tube will notinterfere with the meshing front wheel drive gears while the motorcycleis being steered.

The neck tube of the two-wheel drive motorcycle of the present inventionis preferably cut away in the center to accommodate the meshing gearsthat are supported on bearings within the head tube to keep the bearingsand front wheel drive components aligned along the steering axis. Morespecifically, the neck tube is cut away or severed to create twoseparate sections of neck tube above and below the rotating front wheeldrive gears and components within the head tube. The neck tube sectionsare then supported by needle bearings within the head tube and byclamping power of the fork crowns above and below the head tube. In thatway, the head tube acts as a gear casing located between the upper endsof the fork members and below the handlebars. It is important that thecasing be positioned so as not to interfere with rotation of thehandlebars and fork members.

The front wheel drive shafts descending within the front fork posts ofthe two-wheel drive motorcycle of the present invention are configuredto enable both free motion in the steering of the motorcycle and freerotation of the front tire as well as to create no interference with thedisk brake system. In the first and second embodiments disclosed herein,two series of symmetrical meshing gears within the fork crown transferpower outward from the axis of steering to the drive shafts locatedwithin the fork members on each side of the front wheel. Alternatively,a universal joint system could be utilized.

The front wheel drive system of the two-wheel drive motorcycle of thepresent invention also may include an adjustable component to enable thecompression of the front fork and may also include an adjustablecomponent to accommodate movement of the rear suspension if the frontwheel drive originates at the rear wheel. As in the first embodiment,sliding shafts within the fork tubes could be utilized to accommodatethe expansion and contraction of the shock-absorbing front fork. As inthe seventh embodiment, a ball spline system may provide smoothexpansion and contraction with limited friction as the sliding shaftsexpand and contract. Since the front wheel drive system is under veryhigh torque loads during operation, ball bearing spline shafts or needlebearing square shafts may be utilized to minimize this friction.Alternatively, a telescoping universal joint could be utilized to adjustfor lengthening and shortening of the front fork. Also, numerousalternate drive gear combinations can be used instead of the miter gearsfor transmitting power from the main drive shaft to the front driveshaft system.

The front wheel drive system of the present invention optionallyincludes an engagement clutch located either within the motorcycle'stransmission or at the rear wheel to enable the rider to optionallyshift the two-wheel drive motorcycle from rear-wheel-only drive totwo-wheel drive to, potentially, front wheel only drive if the clutch islocated within the transmission. The engagement clutch for the frontwheel drive could be either a hydrostatic or hydraulic clutch as is wellknow in the industry or a cable-activated mechanical clutch featuringengaging dog tooth plates as shown in the fourth embodiment of thepresent invention.

A free wheeling or one-way front hub utilizing at least one rollerclutch is also disclosed. The roller clutch has the advantage of beingvirtually instantaneous in engaging as the one-way hub reverses from itsfree-wheeling direction to the engaged direction. The free wheeling hubdisclosed herein may also feature a torque limiting clutch to preventfront wheel drive failure upon the transfer of severe torque loadsthrough the drive system.

The front wheel drive system may also include a torque limiting clutchlocated along the shaft of the front wheel drive system between themotor and the head tube that provides for a fail-safe release of excesstorque. The torque limiting clutch may include clutch plates heldtogether by pressure that slip relative to each other whenpre-determined torque levels are exceeded. The plates of the torquelimiting clutch would then re-establish rigid contact with respect toeach other to provide for continued power transfer to the front wheel.

Thus, according to the broad aspects of the invention, the two-wheeldrive motorcycle of the present invention may include:

-   (a) a rigid front wheel drive that transmits power from the engine    and transmission or from the rear wheel to the front wheel, through    a series of rigid drive shafts including a main drive shaft and a    front drive shaft and a series of meshing gears or, alternatively,    through other front wheel drive configurations such as a ball    bearing drive system that would provide similar efficient and    instantaneous power transfer to the front wheel;-   (b) a frame, head tube, steering tube, and front fork constructed of    tubing, including sections which enclose the front wheel drive    system;-   (c) a front wheel drive with components that i) are located on or    very near the steering axis and preferably, within the head tube and    neck tube that have been modified to accommodate the front wheel    drive as it rotates, ii) are designed to minimize torque reactions    due to the rotating shafts, and iii) are designed to accommodate a    full range of steering;-   (d) a pair of front drive shafts positioned symmetrically relative    to the centerline and a pair of front drive shafts located on    opposite sides of the front wheel to counterbalance rotational    torque reactions from the front wheel drive and also configured to    enable both free motion in the steering of the motorcycle and free    rotation of the front wheel without interfering with braking or tire    rotation;-   (e) a front wheel drive with an adjustable component to accommodate    the movement of a shock-absorbing front fork or a rear suspension to    ensure a smoother ride;-   (f) an engagement clutch to provide the rider the option of shifting    the motorcycle from two-wheel drive to rear wheel-only drive;-   (g) a one-way hub in the front wheel resulting in minimal backlash    to enable virtually instantaneous power transfer to the front wheel;-   (h) a torque-limiting clutch to enable release of extreme torque    loads within the front wheel drive prior to failure.

In summary, in the present invention, the power is transferred from theengine of the two-wheel drive motorcycle through a rigid front wheeldrive that includes a series of meshing gears. The frame of themotorcycle is designed to contain the front wheel drive system thattransmits power to the front wheel.

The power is transmitted from the engine to a front wheel drive shaftthat originates either within the transmission or from the rear wheel. Adrive gear at the front end of the main drive shaft meshes with at leastone additional drive gear that is located at or very near the axis ofsteering and along the centerline within the head and steering tube.Additional front wheel drive components along the axis of steeringcancel or minimize the effect of torque generated from the spinningfront wheel drive on the rider's ability to control and steer thetwo-wheel drive motorcycle. Additionally, the neck and head tube arestandard-sized or, alternatively, enlarged in comparison to a standardbicycle to allow for full steering capabilities while transferring powerto the front wheel. The paired rigid front wheel drive then descendssymmetrically along both sides of the front wheel through either aseries of meshing gears that may be located within the fork crown, oralternatively with a universal joint to attach to the front wheel driveshafts. Those skilled in the art will recognize other methods forconstructing a front drive shaft system that does not interfere with thefront wheel, and the embodiments disclosed herein are not to beconstrued as limiting.

The front drive shafts transmit power through shafts along both sides ofthe front wheel within the front fork through the meshing of drive gearsattached to the lower end of each front shaft and gears mountedcircumferentially on each end of the front wheel hub. The front wheelhub may be a one-way hub that catches in one direction but freewheels inthe other direction to enable the rider to coast freely. The front wheelhub could utilize at least one roller clutch to enable one-wayfreewheeling. Roller clutches have the added advantage of silentoperation and nearly instantaneous engagement. While virtually allratcheting hubs feature some degree of backlash as the ratchet engages,the roller clutch engages virtually as soon as the rotational directionof the hub changes. This feature is important for the front wheel driveso that any power transferred through the front wheel drive will resultin instantaneous front wheel traction whereas the use of a ratchetingfront hub would result in some degree of rotational backlash in thefront hub before the front wheel would engage and become powered by thefront wheel drive. Additionally, the use of more than one roller clutchwithin the front hub would provide additional strength in the system byspreading the torque forces over a larger surface within the hub shell.

As disclosed, the front wheel drive system of the present invention maybe completely incorporated into a shock-absorbing front fork of thetwo-wheel drive motorcycle. The sliding front drive shafts slide withinthe meshing gears or, alternatively, an inner sliding shaft and an outersliding shaft within the fork member slide relative to each other withthe change in length of the shock-absorbing front fork. Alternativefront fork designs include the use of expanding ball spline universaljoints in the place of the meshing gears. The complete integration ofthe front wheel drive within the front fork crown and fork members isimportant for both aesthetic appearances of the motorcycle as well asminimizing danger to the rider from exposed rotating parts.Additionally, the enclosure of the front wheel drive within the forktubes keeps the front wheel drive in a fixed position to increaseefficiency of power transfer. Those skilled in the art will recognizeother methods for constructing and mounting a shock-absorbing front forkonto the motorcycle's frame in a manner which does not interfere withsteering or rotation of the front wheel while enabling the front driveshaft system to expand and to contract with the expansion andcontraction of the shock-absorbing front fork.

One embodiment of the two-wheel drive motorcycle of the presentinvention features power transfer directly from the engine andtransmission to the front wheel through a rigid drive system. The rigiddrive system is internal to the motorcycle frame or within tubingattached to the motorcycle frame and within the head tube and steeringtube to enable a full range of steering and instantaneous power transferto the front wheel. Furthermore, in contrast to two-wheel drive bicyclespreviously disclosed, front wheel drive components located symmetricallyrelative to the axis of steering and centerline are important forcontrolling torque reactions while steering or operating the two-wheeldrive motorcycle.

Similar to a two-wheel drive bicycle, the two-wheel drive motorcycle hasincreased traction and mobility of the front wheel, especially duringuphill climbs and downhill cornering on loose or slippery material. Ashock-absorbing front fork and rear suspension ensures a smoother rideand greater contact of the front wheel with the terrain for all-aroundimproved rider experience. The invention discloses a method ofmanufacturing a functional two-wheel drive two-wheeled vehicle with allthe disclosed embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of an embodiment of a two-wheel drivemotorcycle of the present invention with the front wheel driveoriginating directly from a transmission located at the engine.

FIG. 2 is a front view of the front fork for a two-wheel drivemotorcycle of the present invention with symmetrical drive shafts.

FIG. 3 is a side view of the head tube and cut-away neck tube for atwo-wheel drive motorcycle according to the present invention.

FIG. 4 is a top view of the series of meshing gears within the forkcrown of the two-wheel drive motorcycle of the present invention.

FIG. 5 is front view of a one-way front hub with a roller clutch for atwo-wheel drive motorcycle in accordance with the present invention.

FIG. 6 is a side view of the rear wheel and front wheel drive system ofa two-wheel drive motorcycle according to the present invention.

FIG. 7 is a front view of a one-way front hub with a roller clutch for atwo-wheel drive motorcycle in accordance with the present invention.

FIG. 8 is an exploded view of a one-way front hub with a front rollerclutch and including a torque-limiting clutch in accordance with thepresent invention.

FIG. 9 is an exploded view of the engagement clutch for the front wheeldrive of a two-wheel drive vehicle in accordance with the presentinvention.

FIG. 10 is a perspective view of an outer clutch plate of the engagementclutch of FIG. 9.

FIG. 11 is a side view of a two-wheel drive full suspension mountainbike featuring a four-bar linkage front suspension system with anadjustable rake feature.

FIG. 12 is a side view of the rear wheel and front wheel drive system ofa two wheel drive motorcycle featuring a torque limiting clutch alongthe front wheel drive system and further including sliding front shaftsalong the front fork that include ball bearings.

FIG. 13 is a side view of the torque limiting clutch of a two wheeldrive motorcycle.

FIG. 14 is a side view of the sliding shafts of the front wheel drivesystem along the front fork of the two wheel drive motorcycle includingneedle bearings.

FIG. 15 is a top view of the sliding shafts of the front wheel drivesystem along the front fork of the two wheel drive motorcycle includingball bearings.

DETAILED DESCRIPTION First Embodiment of the Invention Illustrating aTwo-Wheel Drive Motorcycle with a Drive System Originating from theEngine and Transmission

FIG. 1 is a side view of the first embodiment of the inventionillustrating a two-wheel drive motorcycle 400 with a motorcycle frontwheel drive 401 (see FIG. 6) originating directly from an engine 402 andmotorcycle transmission 403. FIG. 6 is a side view of the rear wheel andfront wheel drive system of a two-wheel drive motorcycle according tothe present invention. The two-wheel drive motorcycle 400 of the presentembodiment includes a rear wheel 404 and a front wheel 405. The rearwheel 404 further includes a rear wheel hub 406 and the front wheelfurther includes a one-way front wheel hub 407. The rear wheel 404 andrear wheel hub 406 rotate about a rear wheel axle 408 that is attachedto a motorcycle frame. The front wheel 405 rotates about a front wheelaxle 410 that is attached to a motorcycle steering mechanism 411 of thetwo-wheel drive motorcycle 400. The motorcycle frame further includes aforward frame section 412 that includes a pivot point 413 at its rearend and a motorcycle head tube 414 at its forward end. A right rearwheel support arm 415 and a left rear wheel support arm (not shown)pivotally attach at opposite sides of the pivot point. A right supportarm dropout 416 and a left support arm dropout (not shown) on the rightrear wheel support arm 415 and left rear wheel support arm (not shown),respectively, attach to the rear wheel axle 408 and support the rearwheel 404. A rear suspension 417 pivotally attaches between the rightrear wheel support arm 415 and left rear wheel support arm (not shown)and to the forward frame section 412. The rear suspension 417 expandsand contracts to accommodate movement of the rear wheel 404 around thepivot point 413 in order to absorb shock and bumps and provide asmoother ride. Additionally, as is well known in the art, the forwardframe section 412 can include innumerable combinations of frame tubing,bars, and other supporting members to support the engine 402, motorcycletransmission 403, a seat 418, and the motorcycle steering mechanism 411.

As shown in FIGS. 1-3, the motorcycle steering mechanism 411 isrotatably mounted on the forward frame section 412 within the motorcyclehead tube 414 and includes a motorcycle shock-absorbing front fork 419that rotatably attaches the front wheel 405. The motorcycleshock-absorbing front fork 419 adjusts in length to absorb bumps andprovide the rider with a smoother ride. The motorcycle shock-absorbingfront fork 419 further includes a right motorcycle fork tube 420 and aleft motorcycle fork tube 421 that are held in parallel to each other byan upper motorcycle fork crown 422 and a lower motorcycle fork crown423. The upper motorcycle fork crown 422 further supports the motorcyclehandlebars 424 and attaches an upper steering tube 425 which isrotatably supported at its lower end 426 within the motorcycle head tube414 on an upper motorcycle head tube bearing 427. The lower fork crown423 further attaches a lower steering tube 428 which is rotatablysupported at its upper end 429 within the motorcycle head tube 414 on alower motorcycle head tube bearing 430.

The right motorcycle fork tube 420 and left motorcycle fork tube 421further include a right fork dropout 431 and a left fork dropout 432,respectively, that attach the lower ends of each motorcycle fork tube420, 421 to the front wheel axle 410.

In the present embodiment, the engine 402 transfers power to the rearwheel 404 through the motorcycle transmission 403 to an attached firsttransmission drive sprocket 433 that in turn drives a rear drive chain434 and a rear wheel drive sprocket 435 that is attached to and powersthe rear wheel hub 406 and the rear wheel 404. Alternatively, as is wellknown in the art, the rear wheel 404 could be powered by a rear driveshaft (not shown) directly from the transmission to a rear drive gear(not shown) mounted on the rear wheel hub 406.

In the present embodiment of the invention as shown in FIGS. 1-6, theengine 402 transfers power through a motorcycle front wheel drive 401located within the forward frame section 412, the motorcycle head tube414 and the motorcycle shock-absorbing front fork 419 to the front wheel405. More specifically, the engine 402 transfers power through themotorcycle transmission 403 to a second transmission drive sprocket 436.The second transmission drive sprocket 436, in turn, transfers powerthrough a front drive chain 437 to a front drive sprocket 438. A firstfront drive gear 439 mounts circumferentially on the front drivesprocket 438 and transfers power to a second front drive gear 440 thatis attached to the rear end of a main front drive shaft 441. Within themotorcycle head tube 414 of the present embodiment as shown in FIGS. 2and 3, a motorcycle head tube gear 442 attaches at the front end 443 ofthe main front drive shaft 441 and meshes with and transfers power to anupper head tube gear 445 and a lower head tube gear 446.

The main front drive shaft 441 is contained within a main drive tube 447in the present embodiment and is supported at each end with main driveshaft bearings 444. An alternative configuration would eliminate theneed for the main drive tube 447 by supporting the main front driveshaft 441 at each end with the forward frame section 412. Since the mainfront drive shaft 441 is located within the forward frame section 412there is little risk to the rider of danger from the rotating main frontdrive shaft 441 and enclosure within a separate main drive tube 447 maynot be necessary and should not be construed as limiting the presentinvention. Thus, an important consideration for supporting themotorcycle front wheel drive 401 within the forward frame section 412 isthat the front drive sprocket 438 with attached first front drive gear439 and second front drive gear 440 should be firmly held in place toensure smooth and efficient meshing and power transfer to the main frontdrive shaft 441. Additionally, the main front drive shaft 441 should befirmly supported at both ends to enable free rotation, but smoothtransfer of power through the motorcycle head tube gear 442 to the upperhead tube gear 445 and lower head tube gear 446 within the motorcyclehead tube 414.

The use of the second transmission sprocket 436, the front drive chain437 and the front drive sprocket 438 in the present embodiment is not tobe construed as limiting the present invention. The front drive chain437 could easily be replaced by a second front drive shaft (not shown)that receives power directly from the motorcycle transmission 403 andtransmits power to the main front drive shaft 441 through either auniversal joint system (not shown) or through a pair of meshing gears(not shown) attached at the front end of a second front drive shaft (notshown) and rear end of the main front drive shaft 441. One reason forhaving a front drive chain 437 and main front drive shaft 441 is toprovide the appropriate clearance around the engine 402 and gas tank 448or battery (not shown) of the two-wheel drive motorcycle 400.

It is possible, therefore, that certain configurations of the two-wheeldrive motorcycle 400 could feature an alternate configuration for a maindrive shaft (not shown) that transfers power directly from themotorcycle transmission 403 to the motorcycle head tube gear 442.Alternatively, a two-wheel drive motorcycle that transfers powerdirectly from the rear wheel 404 to the motorcycle head tube gear 442 iscontemplated (such as the front wheel drive system shown in FIG. 11).Such a configuration would utilize linkages, chain and sprocketcomponents and telescoping universal joints (not shown) to accommodatemovement of the rear suspension 417 and alternative motorcycle framedimensions and designs. Additionally, an important consideration is thatthe gearing ratio from the engine to the front wheel or from the rearwheel to the front wheel should be adjusted (by varying the number ofgear or sprocket teeth, as is well known in the art) to preferablyresult in a front wheel that is just slightly under-driven with respectto the rear wheel.

The motorcycle head tube gear 442 is located within the motorcycle headtube 414 at or very near the centerline 449 of the two-wheel drivemotorcycle 400 immediately behind the axis of steering 450 of themotorcycle steering mechanism 411. Positioning the motorcycle head tubegear 442 and the front end 443 of the rotating main front drive shaft441 on the center line 449 of the two-wheel drive motorcycle 400 willresult in minimal torque reactions that could effect steering andcontrol. Similarly, the upper head tube gear 445 and lower head tubegear 446 are located within the motorcycle head tube 414 at or very nearthe axis of steering 450 of the motorcycle steering mechanism 411 tominimize or eliminate torque reactions that could effect steering andcontrol.

In transferring power from the main front drive shaft 441 through themotorcycle head tube 414, the upper head tube gear 445 is attached to aninner drive tube 451 and includes an upper end 452 and a lower end 453with the upper end 452 being rotationally supported within the uppersteering tube 425 on an upper steering tube bearing 454 and the lowerend 453 being rotationally supported within the lower motorcycle forkcrown 423. The lower head tube gear 446 is attached to an outer drivetube 455 that includes an upper end 456 and a lower end 457 and isrotationally supported within the lower steering tube 428 at upper end456 on a first lower steering tube bearing 458. A second lower steeringtube bearing 459 provides additional rotation support to the outer drivetube 455. In the present embodiment, the inner drive tube 451 ispositioned within and rotates independently from the outer drive tube455 at or very near the axis of steering 450. Moreover, the lower end453 of the inner drive tube 451 extends through and below the lower end457 of the outer drive tube 455. The number, type, and positioning ofthe support bearings 454, 458, 459 on the inner drive tube 451 and outerdrive tube 455 should not be construed as limiting the present inventionsince any number of bearings adequate to support the motorcycle frontwheel drive 401 within the motorcycle head tube 414 is contemplated.

Since the upper head tube gear 445 and lower head tube gear 446 meshwith the motorcycle head tube gear 442 on opposite sides of themotorcycle head tube gear 442, the upper head tube gear 445, includingthe attached inner drive tube 451, and the lower head tube gear 446,including the attached outer drive tube 455, rotate in oppositedirections relative to each other within the motorcycle head tube 414,below the upper steering tube 425 and above the lower steering tube 428.This configuration enables rotation of the head tube gears 442, 445, 446within the motorcycle head tube 414 and further permits rotation of themotorcycle steering mechanism 411 around the motorcycle front wheeldrive 401. Furthermore, the upper head tube gear 445, including theattached inner drive tube 451, and the lower head tube gear 446,including the attached outer drive tube 455, are located at or very nearthe axis of steering 450 of the motorcycle steering mechanism 411 inorder to minimize and counterbalance the torque reactions caused by therotating motorcycle front wheel drive 401 within the motorcycle headtube 414.

As shown in FIGS. 2 and 4, a first series of meshing crown gears 460,461, 462 are driven by the outer drive tube 455 and a second series ofmeshing crown gears 463, 464, 465 are driven by the inner drive tube451. More specifically, the lower end 457 of the outer drive tube 455attaches a first crown gear 460 that meshes with and drives a secondcrown gear 461, that meshes with and drives a third crown gear 462.Similarly, the lower end 453 of the inner drive tube 451 attaches afourth crown gear 463 that meshes with and drives a fifth crown gear464, that meshes with and drives a sixth crown gear 465.

The positioning of the first series of meshing crown gears 460, 461, 462and the second series of meshing crown gears 463, 464, 465 within thelower motorcycle fork crown 423 serves several purposes: For example,the lower motorcycle fork crown 423 can act essentially as a gear box tohold the meshing crown gears 460, 461, 462, 463, 464, 465 in a fixedposition while enabling free rotation on short gear shafts 497 andsupport bearings (not shown). Also, for example, the lower fork crownencloses the meshing crown gears 460, 461, 462, 463, 464, 465 to reduceexposure of the moving parts that could endanger the rider. Third, thefirst series of meshing crown gears 460, 461, 462, that is driven by theouter drive tube 455 rotates in an opposite and counterbalancingdirection relative to the respective second series of meshing crowngears 463, 464, 465 that is driven by the inner drive tube 451. Themeshing crown gears 460, 461, 462, 463, 464, 465 as shown, are ofhelical or spiral design, however, straight-teeth gears could also beused. The design and configuration of the gears, as disclosed herein,including number of gears, design of meshing teeth, and positioningwithin the steering mechanism is not to be construed as limiting thepresent invention. Moreover, the positioning of the meshing crown gears460, 461, 462, 463, 464, 465 within the lower motorcycle fork crown 423is not to be construed as limiting since they could easily be positionedwithin the upper fork crown 422 or in separate fork gear supports (notshown) in the motorcycle steering mechanism 411 or motorcycleshock-absorbing front fork 419.

Stated more specifically, when viewed from above (the rider'sperspective) as shown in FIG. 4, the first crown gear 460 is driven bythe outer drive tube 455 in a clockwise direction and the fourth crowngear 463 that is driven by the inner drive tube 451 and located directlybelow the first crown gear 460 rotates in a counter-clockwise direction.Both the first crown gear 460 and the fourth crown gear 463 are locatedat or very near the axis of steering 450 and centerline 449 and theopposite rotations of each crown gear 460, 463 would tend tocounterbalance and cancel or minimize the potential torque reactionscaused by rotation of each crown gear 460, 463. Moving away from theaxis of steering 450 and centerline 449 within the lower motorcycle forkcrown 423, the second crown gear 461 is driven in a counterclockwisedirection by the first crown gear 460 while the fifth crown gear 464 isdriven in a clockwise direction by the fourth crown gear 463. Theopposite rotational directions of the second crown gear 461 and fifthcrown gears 464 at symmetrical distances from the axis of steering 450and centerline 449 would tend to counterbalance and cancel or minimizethe potential torque reactions caused by rotation of each crown gear461, 464. Finally, the third crown gear 462 is driven in a clockwisedirection by the second crown gear 461 while the sixth crown gear 465 isdriven in a counterclockwise direction by the fifth crown gear 464. Thethird crown gear 462 and sixth crown gear 465 are positionedsymmetrically farther from the axis of steering 450 and centerline 449within the lower motorcycle fork crown 423 and the opposite rotationaldirections of each crown gear 462, 465 would tend to counterbalance andcancel or minimize the potential torque reactions.

Thus, through opposite rotation and symmetrical positioning relative tothe axis of steering 450 and centerline 449, the counterbalanced crowngear pairs 460 and 463; 461 and 464; 462 and 465, the rotational torqueand moment of inertia is counterbalanced and cancelled or minimizedwithin the lower motorcycle fork crown 423 enabling the rider tomaintain better control of the two-wheel drive motorcycle 400. Thenumber, positioning, and rotational direction of the crown gears 460,461, 462, 463, 464, 465 should not be construed as limiting the presentinvention. Those skilled in the art could easily envision alternatecombinations of meshing crown gears that would have similar symmetricalqualities and counterbalancing configurations.

In the present embodiment, the third crown gear 462 and sixth crown gear465 are located within the right motorcycle fork tube 420 and leftmotorcycle fork tube 421 respectively. The third crown gear 462 issplined on its inner surface and receives a right upper splined end 466of a right fork drive shaft 467 and sixth crown gear 465 has an innersplined surface 496 and receives a left upper splined end 468 of a leftfork drive shaft 469. The fork drive shafts 467, 469 are supportedwithin the motorcycle fork tubes 420, 421 on fork tube bearings 489,490, 491, 492 in a manner that permits rotation of the fork drive shafts467, 469 as well as movement up and down within the crown gears 462, 465but prohibits lateral movement within the motorcycle fork tubes 420,421. In this way, the rotating motorcycle front wheel drive 401 willalso adjust for movement of the motorcycle shock-absorbing front fork419. In an alternative configuration, the splined upper ends 466, 468could be further rotationally supported on bearings or bushings abovethe crown gears 462, 465 to provide additional support within themotorcycle fork tubes 420, 421.

The right splined upper end 466 of the right fork drive shaft 467 slidesinto and is powered by the third crown gear 462, and the left splinedupper end 468 of the left fork drive shaft 469 slides into and ispowered by the sixth crown gear 465 as the motorcycle front wheel drive401 rotates. Moreover, due to the opposite rotation of the third crowngear 462 and sixth crown gear 465, as discussed above, the right forkdrive shaft 467 and left fork drive shaft 469 rotate in oppositedirections within the right motorcycle fork tube 421 and left motorcyclefork tube 422 respectively, thereby counterbalancing and canceling orminimizing the torque reactions and inertia caused by the rotating forkdrive shafts 467, 469.

The right fork drive shaft 467 attaches a right fork drive shaft gear470 that meshes with and drives a right front hub gear 471. Similarly,the left fork drive shaft 469 attaches a left fork drive shaft gear 472that meshes with and drives a left front hub gear 473. As shown in FIGS.2 and 4, the clockwise rotation (as viewed from the rider) of the thirdcrown gear 462, right fork drive shaft 467, and right fork drive shaftgear 470 will cause and result in forward rotation of the right fronthub gear 471 and attached front wheel 405 (relative to the ground).Similarly, the counterclockwise rotation (as viewed from the rider) ofthe sixth crown gear 465, left fork drive shaft 469, and left fork driveshaft gear 472 will cause and result in forward rotation of the leftfront hub gear 473 and attached front wheel 405 (relative to theground).

An alternative embodiment, to enable adjustment of the motorcycleshock-absorbing front fork 419 in response to bumps would be toconfigure the right fork drive shaft 467 and left fork drive shaft 469into two separate sliding sections. The upper sliding sections (notshown) would be attached at the third crown gear 462 and sixth crowngear 465 respectively and would rotate with and slide over the lowersliding sections (not shown) that would be attached to the right forkdrive shaft gear 470 and left fork drive shaft gear 472 respectively.

Thus, in summary, the present embodiment of the two-wheel drivemotorcycle 400 discloses a motorcycle front wheel drive 401 thatincludes components positioned on the axis of steering 450 andcenterline 449 and symmetrically positioned in a counterbalancingfashion relative to the axis of steering 450 within the motorcyclesteering mechanism 411 and motorcycle shock-absorbing front fork 419.Power transferred from the engine 402 through the motorcycletransmission 403 drives the second transmission drive sprocket 436 whichtransfers power through a front drive chain 437 to a front drivesprocket 438. A first front drive gear 439 mounts circumferentially onthe front drive sprocket 438 and meshes with and transfers power to thesecond front drive gear 440 that is attached to and transfers power tothe main front wheel drive shaft 441.

To transfer power through the motorcycle head tube 414 and the leftmotorcycle fork tube 421 via the motorcycle head tube gear 442 attachedto the front end 443 of the main front drive shaft 441 within themotorcycle head tube 414. The motorcycle head tube gear 442 meshes withand transfers power to the upper head tube gear 445 that is attached tothe inner drive tube 451. The lower end 453 of the inner drive tube 451attaches and powers the fourth crown gear 463 that meshes with anddrives the fifth crown gear 464, that meshes with and drives the sixthcrown gear 465. The left splined upper end 468 of the left fork driveshaft 469 slides into and is driven by the rotation of the sixth crowngear 465 to transfer power to the left fork drive shaft 469 that islocated within the left motorcycle fork tube 421. The left fork driveshaft gear 472 is attached to and driven by the left fork drive shaft469, and further, meshes with and drives a left front hub gear 473 thatis attached to and drives the one-way front wheel hub 407 and attachedfront wheel 405.

To counterbalance the transfer of power through the left motorcycle forktube 421, rotational power of the motorcycle front wheel drive 401 istransferred symmetrically through the motorcycle head tube 414 and rightmotorcycle fork tube 420. The motorcycle head tube gear 442 attaches tothe front end 443 of the main front drive shaft 441 within themotorcycle head tube 414 and meshes with and transfers power to thelower head tube gear 446 that is attached to the outer drive tube 455.The lower end 457 of the outer drive tube 455 attaches and powers thefirst crown gear 460 that meshes with and drives the second crown gear461, that meshes with and drives the third crown gear 462. The rightsplined upper end 466 of the right fork drive shaft 467 slides into andis driven by the third crown gear 462 to transfer power to the rightfork drive shaft 467 that is located within the right motorcycle forktube 420. The right fork drive shaft gear 470 is attached to and drivenby the right fork drive shaft 467, and further, meshes with and drives aright front hub gear 471 that is attached to and drives the one-wayfront wheel hub 407 and attached front wheel 405.

As discussed previously, the counteracting rotation and symmetricalplacement of the motorcycle front wheel drive 401 within the motorcycleshock-absorbing front fork 419 relative to the axis of steering 450 andthe centerline 449, thereby counterbalancing canceling or minimizing thetorque reactions and inertia caused by the rotating motorcycle frontwheel drive 401 components is not to be construed as limiting.

Numerous configurations that would place components along the steeringaxis 450 and within the motorcycle head tube 414 are contemplated.Additionally, numerous configurations for varying the number,symmetrical placement, and the direction of counterbalancing rotation ofthe crown gears 460, 461, 462, 463, 464, 465 within the lower motorcyclefork crown 423 is contemplated. While internalizing the motorcycle frontwheel drive 401 within the lower motorcycle fork crown 423, rightmotorcycle fork tube 420 and left motorcycle fork tube 421 is preferred,this configuration should not be construed as limiting because one couldeasily locate certain front wheel drive components external to themotorcycle shock-absorbing front fork 419.

While the present embodiment also features the upper steering tube 425and lower steering tube 428, alternate configurations that enablerotation of the motorcycle steering mechanism 411 around the motorcyclehead tube gear 442, the upper head tube drive gear 445, and the lowerhead tube gear 446 are contemplated, the steering tube could also be asingle unit featuring a cut-away section (not shown) to enable the freerotation of the motorcycle steering mechanism 411 around the meshinghead tube gears 442, 445, 446. Additionally, those skilled in the artwill recognize that alternative drive systems, including a ball bearingdrive system could easily replace chain and shaft front wheel drive.Moreover, the motorcycle front wheel drive 401 could easily originatedirectly from the rear wheel 404 in a configuration similar to thatdisclosed in related applications and as shown in the embodiment of FIG.11.

Second Embodiment of the Invention Illustrating a One-Way Front Hub withRoller Clutch for a Two-Wheel Drive Motorcycle

FIG. 5 is a front view of a one-way front wheel hub 407 for a two-wheeldrive motorcycle 400 with a right roller clutch 475 and a left rollerclutch 476. In the present embodiment, the one-way front wheel hub 407includes a motorcycle outer hub shell 477, a right inner hub shell 478and a left inner hub shell 479. The right inner hub shell 478 furtherincludes a right roller clutch surface 480 and the left inner hub shell479 further includes a left front roller clutch surface 481. In thepresent embodiment, the right inner hub shell 478 and left inner hubshell 479 are separate pieces to enable easy assembly, however, theycould also be a single piece. Alternatively, the right inner hub shell479 and left inner hub shell 480 could each be made of several pieces inorder to accommodate a motorcycle torque-limiting clutch configuration(not shown) similar to the torque-limiting clutch assembly 299 discussedin the third embodiment, below.

The front wheel axle 410 rotationally attaches within the right innerhub shell 478 and left inner hub shell 479 and is supported via a firstfront wheel axle bearing 482 and a second front wheel axle bearing 483.The front wheel axle 410 attaches at each end to the right fork dropout431 and left fork dropout 432 and is held in place within the rightinner hub shell 478 and left inner hub shell 479 by a first front hubend cap 484 and a second front hub end cap 485. A first front hubbearing 486 is positioned between the motorcycle outer hub shell 477 andthe right inner hub shell 478 allowing the motorcycle outer hub shell477 and right inner hub shell 478 to rotate independently whilesupporting the lateral forces of the one-way front wheel hub 407.Similarly, a second front hub bearing 487 is positioned between themotorcycle outer hub shell 477 and the left inner hub shell 479 allowingthe motorcycle outer hub shell 477 and left inner hub shell 479 torotate independently while supporting the lateral forces of the one-wayfront wheel hub 407. The motorcycle outer hub shell 477 further attachesto the front motorcycle wheel 405 as is well known in the art. Themotorcycle outer hub shell 477 also attaches to a motorcycle disk brakerotor 488 as shown in the present embodiment.

The roller clutch 480, 481 is well known in the art and consists ofinner and outer cylinders (not shown) defining an internal space inwhich a series of rollers (not shown) is contained. The inner cylinderfurther includes a series of ramp-like structures (not shown) separatingeach individual roller. During operation of the roller clutch 480, 481,rotation of the inner cylinder in one direction forces the rollers downto the bottom of the ramps and permits the inner cylinder to rotate in adirection opposite the outer cylinder. However, when the inner cylinderof the roller clutch rotates in the other direction the rollers (notshown) roll up the ramp-like structures (not shown) and wedge near thetop of the ramp-like structures of the inner cylinder wedging againstthe outer cylinder. The wedging of the rollers between the inner and theouter cylinders of the roller clutch rotationally locks the innercylinder against the outer cylinder forcing them to rotate together.

The right front hub gear 471 attaches via bolts (not shown) to the rightinner hub shell 478 and the left front hub gear 473 attaches via bolts(not shown) to the left inner hub shell 479. The right roller clutch 475is press fitted into the motorcycle outer hub shell 477 and the rightroller clutch surface 480 of the right inner hub shell 478 slides intothe right roller clutch 475. Similarly, the left roller clutch 476 ispress fitted into the motorcycle outer hub shell 477 and the left rollerclutch surface 481 of the left inner hub shell 479 slides into the leftroller clutch 476. As discussed above, this configuration enables freerotation of the motorcycle outer hub shell 477 relative to the rightinner hub shell 478 and left inner hub shell 479 when the right innerhub shell 478 and left inner hub shell 479 rotate in one directionrelative to the motorcycle outer hub shell 477. However, as described inthe first embodiment, when the right and left fork drive shafts 467, 469and right and left fork drive shaft gears 470, 472 power the right andleft front hub gears 471, 473 respectively, the attached right and leftinner hub shells 478, 479 rotate in the opposite direction and the rightand left roller clutches 475, 476 become rotationally locked resultingin the corresponding rotation of the motorcycle outer hub shell 477 andattached front wheel (not shown). Thus, in this manner, rotational powerthrough the front wheel drive 401 to the right and left front hub gears471, 473 will result in rotation of the right and left inner hub shells478, 479 and the corresponding rotation of the motorcycle outer hubshell 477 and front wheel (not shown) to produce a two-wheel drivemotorcycle 400 driven by both wheels.

A roller clutch hub is uniquely suited for a two-wheel drive motorcyclebecause it transmits power virtually instantaneously to the front wheel.The use of a ratcheting one-way clutch would result in a slight delay intransfer of power to the front when the front wheel is under-driven withrespect to the rear wheel because there are several degrees of backlashbefore the ratchet would engage to power the front wheel.

An additional advantage to using a roller clutch in a front hub, asdisclosed herein, is that since the two-wheel drive motorcycle can beridden in either two-wheel drive or rear-wheel-only drive, the use of aratcheting one-way hub would result in a constant ratcheting sound whenthe front wheel free wheels. Moreover, the present embodiment alsodiscloses the use of at least two roller clutches in the one-way fronthub of the two-wheel drive motorcycle. The use of more than one rollerclutch provides greater surface area to spread the radial forces of thedriven front wheel. The ability to spread the forces along a greatersurface eliminates the need for reinforcement sleeves.

The use and configuration of the one-way front hub 407 with rollerclutches 475, 476 is not to be construed as limiting and alternateconfigurations are envisioned. One alternative configuration wouldutilize a sprag clutch (not shown) in place of the front roller clutches475, 476. Similarly, a torque limiting clutch as shown in the thirdembodiment, below, could be included with the front wheel hub 407 of thetwo-wheel drive motorcycle 400 to reduce the likelihood of motorcyclefront wheel drive 401 failure under extreme toque loads.

Third Embodiment of the Two-Wheel Drive Vehicle Illustrating a One-WayFront Hub with Roller Clutch and Torque Limiting Clutch

FIG. 7 is a front view of a one-way front hub 213 for a two-wheel drivevehicle with a front roller clutch 214. In the present embodiment, theone-way front hub 213 includes an outer front hub shell 215 and an innerfront hub shell 216. The inner front hub shell 216 further includes afront hub roller clutch surface 217. In the present embodiment, theinner front hub shell 216 and front hub roller clutch surface 217 areseparate pieces to accommodate a torque limiting clutch assembly 299discussed below and the inner front hub shell 216 further includes aninner hub spring shaft 312. However, the inner front hub shell 216 withfront hub roller clutch surface 217 could also be a single piece inconfigurations without a torque-limiting clutch assembly 299.

A front axle 59 rotationally attaches within the inner hub shell 216 andis supported via a first front hub axle bearing 218 and near its otherend within the outer hub shell 215 via a second front hub axle bearing219. A third front hub axle bearing 306 may also be utilized to addsupport to the axle within the one-way front hub 213. The front axle 59attaches at each end to the right front dropout 17 and left frontdropout 18 of the front fork (not shown) of the two-wheel drive vehicle(not shown) and is held in place within the hub by a front hub end cap304. A front hub bearing 305 is positioned between the outer hub shell215 and inner hub shell 216 allowing the outer hub shell 215 and innerhub shell 216 to rotate independently while supporting the lateralforces of the one-way front hub 213. The outer front hub shell 215further attaches to the spokes (not shown) of the front wheel (notshown) as is well known in the art. The outer front hub shell 215 mayalso attach to a disk brake rotor 300 as shown in the presentembodiment.

The front bevel gear 32 attaches via bolts (not shown) to the innerfront hub shell 216. A front roller clutch 214 is press fitted into theouter front hub shell 215. The front hub roller clutch surface 217slides into the front roller clutch 214. As discussed above, thisconfiguration enables free rotation of the outer front hub shell 215relative to the inner front hub shell 216 when the inner front hub shellrotates in one direction. However, when pinion gear 31 of the frontwheel drive (not shown) powers the front bevel gear 32, the attachedinner front hub shell 216 rotates in the opposite direction and thefront roller clutch 214 becomes rotationally locked resulting in thecorresponding rotation of the outer front hub shell 215 and attachedfront wheel (not shown). Thus, in this manner, rotational power throughthe front wheel drive (not shown) to the front bevel gear 32 will resultin rotation of the inner front hub shell 216 and the correspondingrotation of the outer front hub shell 215 and front wheel (not shown) toproduce a bicycle driven by both wheels.

FIG. 8 features a disassembled view of the one-way front hub 213 with afront roller clutch 214 and also illustrating a torque-limiting clutchassembly 299. As illustrated, the inner hub shell 216 includes a firstangled pressure plate 301 and the front hub roller clutch surface 217includes a second angled pressure plate 302. These pressure plates fitinternally to the standard one-way front hub 213. This configurationenables the front wheel drive (not shown) to rotate independently fromthe front wheel (not shown) in the event that extreme torque loads aretransferred through the front wheel drive so that they can be relievedwithout damage to the system.

In the present embodiment, the first angled pressure plate 301 iscircumferentially molded to the inner hub shell 216. The second angledpressure plate 302 is molded to the front hub roller clutch surface 217.The first angled pressure plate 301 abuts the second angled pressureplate 302 and is held in constant static contact with the second angledpressure plate 302 by an adjustable pressure plate spring 303. A firstpressure plate spring end 309 of the adjustable pressure plate spring303 is positioned within, and applies pressure at the inner pressureplate surface 307 of the front hub roller clutch surface 217 while asecond pressure plate spring end 311 of the adjustable pressure platespring 303 attaches to an adjustable pressure plate spring stop 308 thatattaches to the end of the inner hub spring shaft 312. In the presentembodiment, the adjustable pressure plate spring stop 308 screws intoposition onto the inner hub spring shaft 312 thus making the tension ofthe adjustable pressure plate spring 303 adjustable depending upon howfar the adjustable pressure plate spring stop 308 is screwed onto theinner hub spring shaft 312. The adjustable pressure plate spring stop308 is rotationally supported against the outer front hub shell 215 bythe front hub bearing 305 and the inner hub spring shaft 312 isrotationally supported on the front axle 59 by the third front hub axlebearing 306.

The constant contact of the first angled pressure plate 301 with thesecond pressure plate 302 enables the transfer of rotational forces fromthe front bevel gear 32 through the inner hub shell 216 and torquelimiting clutch assembly 299, through the front roller clutch 214, tothe outer hub shell 215 to drive the front wheel 17. However, upon thetransfer of a severe rotational torque load through the front wheeldrive (not shown) that may otherwise cause breakage of certain frontwheel drive parts, the rotational torque overcomes the static contact ofthe first angled pressure plate 301 against the second angled pressureplate 302 forcing the first angled pressure plate 301 to slip relativeto the second angled pressure plate 302 by causing a shortening of theadjustable pressure plate spring 303. Severe drive system torque is,therefore, relieved and the first angled pressure plate 301 and secondangled pressure plate 302 resume their static contact due to thepressure from the adjustable pressure plate spring 303.

A roller clutch hub is uniquely suited for a two-wheel drive vehiclebecause it transmits power virtually instantaneously and silently to thefront wheel. The use of a ratcheting one-way clutch would result in aslight delay in transfer of power to the front wheel when the rear wheelslips because there are several degrees of backlash before the ratchetwould engage to power the front wheel.

An additional advantage to using a roller clutch in a front hub, asdisclosed herein, is that since the two-wheel drive vehicle can beridden in either two-wheel drive or rear-wheel-only drive, the use of aratcheting one-way hub would result in a constant ratcheting sound whenthe front wheel free wheels. Moreover, the second embodiment alsodiscloses the use of at least two roller clutches in the one-way frontwheel hub 407 of the two-wheel drive motorcycle 400. The use of morethan one roller clutch provides greater surface area to spread theradial forces of the driven front wheel. The ability to spread theforces along a greater surface eliminates the need for reinforcementsleeves resulting in lighter hubs.

The use and configuration of the one-way front hub 213 with a rollerclutch 214 and torque limiting one-way front hub clutch assembly 299 isnot to be construed as limiting and alternate configurations areenvisioned. One alternative configuration would utilize a sprag clutch(not shown) in place of the front roller clutch 214. Additionally, morethan one roller clutch 214 could be included within the one-way fronthub 213. Similarly, a torque limiting clutch 299 could be included withthe front wheel hub 407 of the two-wheel drive motorcycle 400 to reducethe likelihood of motorcycle front wheel drive 401 failure under extremetoque loads.

For the one-way front hub 213, the outer front hub shell 215 and innerfront hub shell 216 may be made of aluminum or any other light-weightmetal capable of withstanding the axial and rotational forces generatedby rotation of the one-way front hub 213 and the use of any particularmaterial should not be considered as limiting to the present invention.Additionally, reinforcing sleeves around the outer front hub shell 215are not necessary in the present embodiment. Finally, numerousconfigurations for the torque limiting clutch 299 are envisioned and theuse of pressure plates 301, 302 and pressure plate springs should not beconstrued as limiting the mechanisms by which severe front wheel drivetorque can be relieved.

Fourth Embodiment of the Two-Wheel Drive Vehicle Illustrating the FrontWheel Drive Engagement Clutch

Referring to FIG. 9, the fourth embodiment of a two-wheel drive vehicleincorporates an engagement clutch 220 into the front wheel drive (notshown). The engagement clutch 220 provides the rider the option ofoperating the two-wheel drive bicycle in two-wheel drive mode when theengagement clutch 220 is engaged, or alternatively, in rear-wheel-onlydrive mode when the engagement clutch 220 is disengaged. In aconfiguration similar to the present embodiment, an engagement clutch220 could be utilized with the two-wheel drive motorcycle 400 and eithermounted on the motorcycle front wheel drive 401 at the engine 402 andmotorcycle transmission 403 or on the rear wheel 404 (if a direct frontwheel drive from the rear wheel 404 is used). Additionally, a hydraulicor hydrostatic engagement clutch, as is well known in the art could beutilized to enable the rider of the two-wheel drive motorcycle 400 toshift from rear-wheel only drive to two-wheel drive. In a two-wheeldrive motorcycle 400 with front wheel drive 401 originating at theengine 402, and transmission 403, the engagement clutch 220 could beused to provide a motorcycle with rear-wheel-only drive,two-wheel-drive, or in certain conditions, front-wheel only drive byshifting the clutch to a setting that powers only the front wheel drive401 and front wheel 405.

FIG. 9 illustrates a disassembled view of the engagement clutch 220mounted on the one-way rear hub 200 of the two-wheel drive vehicle (notshown). As disclosed in the present embodiment, the entire engagementclutch 220 would fit in the space between the one-way rear wheel hub 200and the left rear dropout (not shown) thus enabling use of standardframe spacing, standard rear hub dimensions, and standard bicyclecomponents.

In the present embodiment as shown in FIG. 9, an inner clutch plate 221attaches via bolts 222 to the disk brake mounting surface 204 of theouter hub shell 202. A clutch bearing 223 is press fitted onto the innerclutch plate's 221 outer edge 224 and a rear gear ring 225 is pressfitted onto the clutch bearing 223 so that the inner clutch plate 221and rear gear ring 225 rotate independently on the clutch bearing 223.Additionally, a flat needle bearing (not shown) may be placed betweenthe inner clutch plate 221 and the rear gear ring 225 to support lateralforces within the engagement clutch 220. The inner edge 226 of the reargear ring 225 is designed to receive an outer clutch plate 227. Theouter clutch plate 227 has a series of rear gear ring stops 228 that fitinto the series outer clutch plate receptors 229 on the inner edge 226of the rear gear ring 225. Alternatively, the rear gear ring stops 228and outer clutch plate receptors 229 could be replaced by any male andfemale spline configuration that would allow the outer clutch plate 227and rear gear ring 225 to slide relative to each other. When assembled,the rear gear ring 225 and outer clutch plate 227 rotate in unison dueto the positioning of the rear gear ring stops 228 of the outer clutchplate 227 within the outer clutch plate receptors 229 of the rear gearring 225. The outer clutch plate 227 is held in place by a snap ring 230inserted into a snap ring slot 231 of the rear gear ring 225.

The inner clutch plate 221 further includes a series of inner dog teeth233 that face the outer clutch plate 227 when the engagement clutch 220is assembled. Similarly, the outer clutch plate 227 further includes aseries of outer dog teeth 234 that face the inner clutch plate 221 whenthe engagement clutch 220 is assembled. Each inner dog tooth 233 furtherincludes a flat facing surface 235 and each outer dog tooth 234 furtherincludes an opposing flat facing surface 236. Finally, the inner clutchplate 221 and outer clutch plate 227 are held apart when the engagementclutch 220 is assembled but not engaged by a circular clutch spring 237that rests circumferentially along on the spring surface 232 of the rearbevel ring gear 225. The entire engagement clutch is positioned betweenthe disk brake mounting surface 204 of the outer hub shell 202 and theleft dropout 8 where the rear drive bevel gear 37 is positioned. FIG. 10illustrates an alternate view of the outer clutch plate 227 showing therear gear ring stops 228, the outer dog teeth 234, and the opposing flatfacing surfaces 236.

Engagement of the engagement clutch 220 in the present embodiment isfacilitated by a cable-actuated external shifting mechanism (not shown).To engage the engagement clutch 220, the rider shifts a cable actuationlever (not shown) on the steering mechanism (not shown). The resultingmovement of the cable forces the external shifting mechanism against theouter clutch plate 227 which moves toward the inner clutch plate 221,compressing the circular clutch spring 237. When the outer clutch plate227 and inner clutch plate 221 fully interlock, the opposing flat facingsurfaces 236 of the outer dog teeth 234 on the outer clutch plate 227come into contact with the flat facing surfaces 235 of the inner dogteeth 233 on the inner clutch plate 221 resulting in the engagement ofthe engagement clutch 220.

When the engagement clutch 220 is engaged, the front wheel driveoperates to transfer power to the front wheel 17 as follows: Power istransferred from the rear drive sprockets (not shown) through theone-way rear hub (not shown). Rotation of the outer hub shell 202 powersthe inner clutch plate 221 which transfers power through the flat facingsurface 235 of inner dog teeth 233 to the opposing flat facing surfaces236 of the outer dog teeth 234 of the interlocked outer clutch plate227. The outer clutch plate 227 then transfers power to the rear gearring 225 due to the interlocking of the rear gear ring stops 228 of theouter clutch plate 227 with the outer clutch plate receptors 229 of therear gear ring 225. The rear gear ring 225 then transfers power to thefront wheel drive (not shown) through the meshing drive shaft piniongear (not shown) and straight main drive shaft (not shown). When theengagement clutch 220 is not engaged (the two-wheel drive bicycle isbeing operated in rear-wheel drive mode), the inner dog tooth gears 233of inner clutch plate 221 and outer dog tooth gears 234 of the outerclutch plate 227 are forced apart by the circular clutch spring 237 andno power is transferred through the front wheel drive.

The disclosed engagement clutch 220 for the two-wheel drive vehicle isnot to be construed as limiting the present invention. Those skilled inthe art will recognize alternative designs that can be incorporated intothe two-wheel drive vehicle, including placement of the engagementclutch assembly on the front hub of the vehicle. The clutch plates 221,227 themselves could feature pressure plates or other alternatives tothe dog-tooth gears disclosed herein. Additionally, the clutch plates221, 227 may be made of light-weight aluminum and may be hard-coatanodized to increase strength. The engagement clutch 220 could also bepositioned on the same side of the one-way rear hub as the rear drivesprockets (not shown). Additionally, the present embodiment uses acircular wave spring 237 to hold the inner and outer clutch plates 221,227 apart. However, a variety of circular springs could be utilized.Finally, while the dimensions of an engagement clutch that fits withinthe standard rear wheel spacing is critical to the broadest applicationof standard industry equipment, including hubs and disk brake systems,alternative hub spacings are envisioned.

Fifth Embodiment of the Two-Wheel Drive Vehicle Featuring a Four-BarLinkage Front Suspension for a Two-Wheel Drive Vehicle into the FrontFork Member

FIG. 11 shows a view of a two-wheel drive vehicle 131 featuringintegration of the front wheel drive into a four-bar linkage frontsuspension 132. This particular configuration is a popular design andcould also be utilized, with slight modification, on a two-wheel drivemotorcycle. Modifications would include the addition of meshing gearsand symmetrical drive shafts, gears and components in the steeringmechanism and front fork drive tubes as disclosed in the firstembodiment. Additionally, components of the front wheel drive for thefour-bar linkage front suspension 132 shown in FIG. 11 are integratedinto the left linkage fork member 137. The four-bar linkage frontsuspension 132 also features a left rake adjuster bar 134 and a rightrake adjuster bar (not shown) that allow the rider to adjust the rake(fork angle relative to the ground) of the two-wheel drive bicycle 131depending upon riding conditions.

The four-bar linkage front suspension 132 is well known in the bicycleand motorcycle industries for its ability to absorb shock more into theframe of the vehicle and less into the steering mechanism and, thus,into the arms and shoulders of the rider. The front wheel drive includesa rear bevel gear 37 mounted on the rear hub 142 that meshes with anddrives a drive shaft pinion gear 38 mounted on the rear end of the reardrive shaft 122. A telescoping rear ball spline universal joint system113 attaches the front end of the rear drive shaft 122 to the rear endof a front linkage drive shaft 135. The front linkage drive shaft 135includes a first front linkage drive gear 136 at its front end.

The four-bar linkage front suspension 132 of the fifth embodiment doesnot include a typical head tube configuration as shown in the previousembodiments. Rather, the four-bar linkage front suspension 132 ispivotally attached directly to the front end of the down drive tube 118and the upper ends of the left fork post 133 and right fork post (notshown) via the left rake adjuster bar 134 and right rake adjuster bar(not shown) respectively. The linkage fork crown 138 then pivotallyattaches with a ball and socket joint 139 to left front linkage arm 140and right front linkage arm (not shown) and attaches the lower ends ofthe left fork post 133 and right fork post (not shown) to the upper endsof the left linkage fork member 137 and right linkage fork member (notshown) respectively.

The lower ends of the left linkage fork member 137 and the right linkagefork member (not shown) then attach to the front hub 141 at the leftlinkage fork dropout 143 and right linkage fork dropout (not shown). Asillustrated, the “four-bar” linkage front suspension 132 forms aparallelogram and includes as its four “bars,” the pivotable attachmentof i) the front end of the down drive tube 118 to ii) the left rakeadjuster bar 134 and the right rake adjuster bar (not shown) to iii) theupper ends of the left fork post 133 and the right fork post (not shown)respectively, and iv) the linkage fork crown 138 to the left frontlinkage arm 140 and right linkage arm (not shown) which then pivotallyconnect to the down drive tube 118.

In the present embodiment of the two-wheel drive vehicle 131, the firstfront linkage drive gear 136 meshes with and powers a second frontlinkage drive gear 144 located at the front end of the down drive tube118 within the steering mechanism support casing 145 and immediatelybehind the steering mechanism support casing 145. The first frontlinkage drive gear 136 and second front linkage drive gear 144 interfacevery close to the axis of steering within the front end of the downdrive tube 118 proximate the steering mechanism 130 and within thesteering mechanism support casing 145.

The proximity of the first front linkage drive gear 136 and second frontlinkage drive gear 144 to the steering mechanism 130 and steeringmechanism support casing 145 acts to minimize any torque reactionsresulting from the rotation of the front wheel drive. Additionally, inthe present embodiment, the first front linkage drive gear 136 andsecond front linkage drive gear 144 mesh at a 90 degree angle. However,meshing angles less than 90 degrees and more than 90 degrees are easilycreated and a 90 degree meshing angle should not be construed aslimiting to the present invention.

The second front linkage drive gear 144 delivers power to the frontwheel 17 through a short connecting shaft 92, a telescoping linkage ballspline universal joint system 146, the internal front linkage driveshaft 147 to an attached front linkage drive shaft gear 148. The frontlinkage drive shaft gear 148 then meshes with and drives the front bevelgear 32 which drives the front wheel 17. The telescoping linkage ballspline universal joint system 146 attaches to the second front linkagedrive gear 144 through the short connecting shaft 92 very close to theaxis of steering to minimize any torque reactions which would negativelyaffect steering. Additionally, an expandable universal joint systemcould be utilized in the front wheel drive of the four-bar linkage frontsuspension 132. Finally, a short connecting shaft 92 may be unnecessaryin certain configurations featuring the telescoping front ball splineuniversal joint system 146 attached directly to the second front linkagedrive gear 144.

An additional aspect of the two-wheel drive vehicle 131 shown in FIG. 11is that the internal front linkage drive shaft 147 is enclosed withinthe left linkage fork member 137. Additionally, pivotally attached atthe upper end of the left fork post 133 and right fork post (not shown)is a left rake adjuster bar 134 and right rake adjuster bar (not shown)respectively. Each rake adjuster bar has at least two front rakeadjustment locations: a front rake adjustment location 149, and a rearrake adjustment location 150 to which the left fork post 133 and rightfork post (not shown) can be optionally attached in order to enable therider to adjust the rake of the two-wheel drive vehicle. By moving thelocation of the left fork post 133 and right fork post (not shown) fromtheir respective front rake adjustment location 149 to the respectiverear rake adjustment location 150 the rider can adjust the rake of thefront fork to adapt to the riding conditions.

The disclosed adaptation of the front wheel drive for the two-wheeldrive motorcycle to the four-bar linkage front suspension is not to beconstrued as limiting the present invention. Those skilled in the artwill recognize alternative designs for linkage suspensions andcorresponding locations of the front wheel drive. Additionally, thenumber of rake adjustment holes is not to be construed as limiting andeach rake adjuster bar could easily consist of three or more rakeadjustment holes.

Sixth Embodiment of the Two-Wheel Drive Vehicle Illustrating a TorqueLimiting Clutch Operatively Engaged with the Front Wheel Drive SystemShaft

FIG. 12 is a side view of the rear wheel and front wheel drive system ofa two wheel drive motorcycle 500 featuring a torque limiting clutch 501.FIG. 13 is a side view of one example of a torque limiting clutch 501that can be positioned along the front wheel drive system of the twowheel drive motorcycle 500. In the present embodiment, the torquelimiting clutch 501 transfers power from a rear clutch drive shaft 502to the rear clutch plate 504. The rear clutch plate 504 is in constantfrictional contact with a front clutch plate 505 that is attached to thefront clutch drive shaft 503.

Additionally, the rear clutch plate 504 and front clutch plate 505 areheld in frictional contact with each other in a fashion where rotationof the rear clutch plate 504 causes rotation of the front clutch plate505. This frictional contact results from the constant pressure of aspring 510 pushing the front clutch plate 505 against the rear clutchplate 504. The tension of the spring 510 is adjusted via tightening anadjustment nut 511 that is located on the front clutch drive shaft 503.As is well known by those familiar with these types of torque limitingdevices tightening the adjustment nut 511 allows the torque limitingclutch 501 to be adjusted for various torque levels.

In the present embodiment, the torque limiting clutch 501 is locatedbetween the front drive gear 440 and the main drive gear 442. Power istransferred through the rotating front drive gear 440 to a rear clutchdrive shaft 502 which is attached to the rear clutch plate 504. Constantfrictional contact between the rear clutch plate 504 and the frontclutch plate 505 cause the front clutch drive shaft 503 to rotate andtransfer power to the head tube gear 442 and then to the front wheeldrive system as described in the earlier embodiments.

As is well known in the art, the torque limiting clutch 501 can beadjusted to so that the rear clutch plate 504 slips relative to thefront clutch plate 505 when excess power is transferred from the engine402 through the front wheel drive system to the front wheel 405 of thetwo wheel drive motorcycle. In this fashion, the torque limiting clutch501 acts as a fail-safe device to prevent catastrophic failure of thedrive system. In alternative embodiments the torque limiting clutch 501could be located between the front drive sprocket 438 and front drivegear 439 of the front wheel drive system. Finally, numerousconfigurations for the torque limiting clutch 501 are envisioned and theuse and location of clutch plates 504, 505 and should not be construedas limiting the mechanisms by which extreme front wheel drive torque canbe relieved. Any type of torque limiting clutches in addition to thosediscussed above, including but not limited to ball detent or springdetent torque limiting clutches may be used for this application, as iswell known by those skilled in the art.

Seventh Embodiment of the Two-Wheel Drive Vehicle IllustratingBearing-Supported Sliding Front Shafts

FIG. 14 is a side view the sliding shafts 506, 507 of a the front wheeldrive system of the two wheel drive motorcycle 500 that feature animproved method of sliding. FIG. 12 is a side view of the same slidingshafts 506 and 507 as they are found in the front wheel drive systemlocated along the right side of the two wheel drive motorcycle, along orcollocated with the front fork. A similar set of sliding shafts (notshown) would be located long the left side of the two wheel drivemotorcycle.

In the present embodiment, the upper sliding shaft 506 slides over theend of the lower sliding shaft 507 while transmitting the rotationalpower of the front wheel drive system to the front wheel as described inthe previous embodiments. The ability of the upper sliding shaft 506 toslide smoothly over the lower sliding shaft 507 with minimal friction iscritical to the smooth operation of the telescoping front fork of themotorcycle. As an improved feature over the splined shafts 466, 467described in the earlier embodiments, FIG. 14 shows the placement of aseries of needle bearings 508 between of upper sliding shaft 506 and thelower sliding shaft 507. The needle bearing act to minimize the frictionthat may otherwise occur between the sliding shafts 506 and 507 whenrotational power is transferred through the front wheel drive system.Alternatively, as shown in FIG. 15, ball bearings 509, may be placedbetween the upper sliding shaft 506 and lower sliding shaft 507 toproduce a similar friction-reducing effect on the expansion andcontraction of the front wheel drive system during operation. In someembodiments of the invention, the sliding shafts 506, 507 can bepositioned within the front fork or adjacent the front fork.

Finally, numerous configurations of bearing-supported sliding shaftsystems and splined shaft systems as well as the use of other bearing orfriction-reducing mechanisms are envisioned and the use and location ofbearings and sliding shafts to reduce friction along the front wheeldrive system should not be construed as limiting the mechanisms by whichsmooth operation of the motorcycle front fork can be achieved.

In considering this invention, it should be remembered that the presentdisclosure is only illustrative, and the scope of the invention is notintended to be limited to the embodiments disclosed herein. Thisinvention discloses both the design and the construction of a two-wheeldrive vehicle with a shock-absorbing front fork and rear suspensionwherein the front wheel drive is entirely enclosed within the frontfork. Additional embodiments disclose aspects of the front wheel drivethat include a one-way front hub using a roller clutch, an engagementclutch, and a torque limiting clutch.

Importantly, the embodiments and inventions disclosed herein are usefuland may be incorporated interchangeably into other embodiments. Toillustrate the numerous scenarios, the two-wheel drive motorcycle 400could also feature a front four-bar linkage suspension disclosed in thefifth embodiment of FIG. 11. Also, the one-way front hub with rollerclutch 213 including a torque-limiting clutch 299 at its front wheel 17,as shown in the third embodiment could be utilized on the two-wheeldrive motorcycle shown in the first and second embodiments. Also, whileit is not common for a motorcycle to have a single crown fork, a singlecrown fork could also be adapted for application on other two-wheeledvehicles.

In accordance with the present invention, the transfer of the power fromthe center drive transmission or the rear wheel is accomplished througha rigid drive system, internal to the vehicle frame that enables a fullrange of steering, maintains vehicle aesthetics, and prevents riderinjury from exposed front wheel drive parts. Importantly, positioning offront wheel drive components on the axis of steering and in asymmetrical and counterbalancing fashion relative to the centerlinewithin the head tube, lower crown and fork tubes minimizes torquereactions from the rotation of the front wheel drive as the front wheelis driven. Furthermore, the rigid shaft system provides virtuallyinstantaneous power transfer to the front wheel for any two-wheeledvehicle.

A two-wheel drive two-wheeled vehicle would have increased traction andmobility of the front wheel, especially during uphill climbs anddownhill cornering on loose or slippery material. The shock-absorbingfront fork and rear suspension ensures a smoother ride and greatercontact of the front wheel with the terrain for all-around improvedrider experience. The engagement clutch further enhances the utility ofthe front wheel drive providing the rider the option of rear-wheel-onlyor two-wheel drive. The invention discloses an excellent method ofmanufacturing a functional two-wheel drive two-wheeled vehicle, and inparticular, a two-wheel drive motorcycle with all the disclosedembodiments. As envisioned, this fully integrated front wheel drivewould not only compete with the most advanced vehicles on the market butwould also create an entirely new category in numerous industries.

While the foregoing is directed to the first through fifth embodimentsof the present invention, other and further embodiments of the inventionmay be devised without departing from the basic scope thereof, whichscope is determined by the claims that follow.

1. A two-wheel drive vehicle, comprising: a frame, the frame including ahead tube; an engine coupled to the frame; a steering mechanismpivotably coupled to said head tube; a rear wheel rotatably coupled tosaid frame; a front wheel rotatably coupled to said steering mechanism;a rear wheel drive assembly configured to transmit power from the engineto the rear wheel; a front wheel drive assembly configured to transmitpower from the engine to the front wheel, at least a portion of saidfront wheel drive assembly being located in said head tube, said frontwheel drive assembly including a torque-limiting clutch.
 2. Thetwo-wheel drive vehicle of claim 1, wherein said torque-limiting clutchis operatively coupled to the front wheel drive assembly between theengine and the head tube.
 3. The two-wheel drive vehicle of claim 2,wherein said torque-limiting clutch includes at least two clutch plates.4. A front wheel drive mechanism for a two-wheel drive vehicle, thefront wheel drive mechanism configured to transmit power from an engineto a front wheel, the front wheel drive mechanism comprising: anadjustable drive mechanism configured to accommodate a movement of afront fork, the adjustable drive mechanism including a rotating firstshaft, a rotating second shaft, at least a portion of said rotatingsecond shaft being disposed within said first shaft, and a plurality ofbearings located between the rotating first shaft and the rotatingsecond shaft.
 5. The front wheel drive mechanism of claim 4, wherein thebearings are ball bearings.
 6. The front wheel drive mechanism of claim4, wherein the bearings are needle bearings.
 7. The front wheel drivemechanism of claim 4, wherein the rotating first shaft and the rotatingsecond shaft are collocated with a front fork of said two wheel drivevehicle.
 8. A front wheel drive mechanism for a two wheel drive vehicleconfigured to transmit power from an engine to a front wheel, the frontwheel drive mechanism comprising: a free-wheeling front hub, saidfree-wheeling front hub including at least two roller clutches, rotationof the front wheel drive mechanism configured to engage said rollerclutches, said roller clutches configured to rotate the front wheel.